Lets learn how to update MongoDB document using update() method.
test database, names collection
1 2 3 4 5 6 | > db.names.find().pretty()
{
"_id" : ObjectId("53c3c4b1a0eddb0a706e4f56"),
"name" : "Satish",
"age" : 27
} |
Observe the document, with fields name and age. We’ll be illustrating update() method by working on this document.
1 2 3 4 5 | > db.names.update({"name": "Satish"}, {"age": 28});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.names.find().pretty()
{ "_id" : ObjectId("53c3c4b1a0eddb0a706e4f56"), "age" : 28 } |
update() method takes at least 2 arguments. First argument being the condition(WHERE clause in sql) and the second argument being the fields to be updated. Observe that, whatever the fields we specify in the second argument are only retained(along with _id), all other fields will be erased.
1 2 3 4 5 6 7 8 9 | > db.names.update({"age": 28}, {"name": "Satish", "age": 28});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.names.find().pretty()
{
"_id" : ObjectId("53c3c4b1a0eddb0a706e4f56"),
"name" : "Satish",
"age" : 28
} |
Now we’ve updated with name as well as age field and it reflects in the document in the collection.
Update Method: MongoDB
[youtube https://www.youtube.com/watch?v=6LfvsoqRoP8]
1 2 3 4 5 6 7 8 9 10 | > db.names.update({"age": 28}, {"name": "Satish", "age": 28, "salary": 200000});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.names.find().pretty()
{
"_id" : ObjectId("53c3c4b1a0eddb0a706e4f56"),
"name" : "Satish",
"age" : 28,
"salary" : 200000
} |
If we want to update/add a new field to the document, we must also specify all other fields we want to retain in the document.
1 2 3 4 5 | > db.names.update({"age": 28}, {"salary": 300000});
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.names.find().pretty()
{ "_id" : ObjectId("53c3c4b1a0eddb0a706e4f56"), "salary" : 300000 } |
If we forget to specify other fields, then they will be erased(except _id field).